The invention is directed to a composition and process for the electrolytic deposition of gold and gold alloy coatings out of an electrolyte that contains or consists of a salt melt.
Gold and gold alloy coatings are in use in many areas of the art in order to enable objects or to protect them from the influence of corrosion. Gold and gold alloy coatings are used especially for electrical contacts in the low-voltage current art and in the semi-conductor industry. In the previously customary wet galvanic process indeed only high carat gold coatings guarantee a sufficient resistance to tarnish and therewih a constant low electric resistance of the contacts to the passage of current.
Because of the high price of gold, for industrial uses for reasons of economy it would be desirable to employ low carat gold alloy coatings which would have to be the equal of the high carat coatings in regard to their resistance to tarnish.
Such wet galvanic depositing low carat gold alloy coatings (&lt;20 carats) however, are for the most part not equal to the high requirements in industrial use. The reasons for the lack of tarnish resistance of these coatings probably is due to the fact that the deposits are heterogeneous and under these conditions of operation there are only partially built mixed crystals from the alloy components, which alone would guarantee a sufficient resistance to tarnishing.
Therefore it was the problem of the present invention to develop a process for the electrolytic deposition of gold and gold alloy coatings with which low carat gold coatings also permit the production of low carat gold coatings having higher resistance to tarnishing in air or other medium.